This study examined the effects of six weeks of velocity specific isokinetic training on peak torque (PT), and the estimated cross-sectional area of the upper arm (AG) in the trained. Thirty volunteers (M=15, F=15) were randomly assigned to an experimental, slow velocity group (S), 60 degrees-per-second (n=9; 25.4±..6.5yr), a fast velocity group (F), 450 degrees-per-second (n=ll, 23.7 ±..S.4yr), or control group (C) (n=10, 26 ± 3.2yr). One limb was randomly selected for isokinetic training (3 d/wk-elbow flexion) using a Biodex System 2 isokinetic dynamometer. The contralateral limb served as a control and as the basis for measurements measure of cross education (CE). Both experimental conditions (S) and (F) were assigned equal training workloads, calcu1ated from an isokinetic pre-test. Pre- and post-tests (PT) were recorded for both limbs at the training velocities of 60 and 450 degrees-per-second, as well as the velocity of 210 degrees-per-second. Pre and post-test (AG's) were measured on the training limb. The (S) condition was significantly different in strength gains from the control at 60 degrees-per-second, but not different from the fast velocity group in the trained limb. The (F) condition was significantly different in strength gains from the control at 450 degrees-per-second, but not different from the slow velocity group in the the trained limb. The conditions were not significantly different from each other in the trained limb at the test velocity of 210 degrees-per-second. The three conditions significantly different from each at the test velocity of 60 degrees-per-second in the trained limb. The conditions did not differ in strength at velocities of 210 and 450 degrees-per-second in the trained limb. The conditions did not differ in the cross-sectional area of the upper arm in the trained limb. The (S) and (F) training conditions improved (PT) by 12.36% and 18.84% at their respective training velocities of 60 and 450 degrees-per-second. These improvements were significantly (p<.05) larger than (C). The (S) and (F) training conditions also increased (PT) by 11.56% and 11.24% at the non-training velocity of 210 degrees-per-second (p<.05). Significant 10.77% (p<.05) improvement in (AG) was recorded in the (S) condition. No changes in (PT) were recorded in the contralateral limb within the three conditions. These data support the concept of limited (S) and (F) hi-directional (PT) overflow and (S) velocity hypertrophy enhancement. The presence of cross education (CE) was not supported by this investigation. / Master of Science

No / Catecholamines that accompany acute physiological stress are also involved in mediating the development of hypertrophy and failure. However, the cellular mechanisms involved in catecholamine-induced cardiac hypertrophy, particularly Ca2+ handling, are largely unknown. We therefore investigated the effects of cardiac hypertrophy, produced by isoprenaline, on INa/Ca and sarcoplasmic reticulum (SR) function in isolated myocytes. Methods: INa/Ca was studied in myocytes from Wistar rats, using descending (+80 to ¿110 mV) voltage ramps under steady state conditions. Myocytes were also loaded with fura-2 and either field stimulated or voltage clamped to assess [Ca2+]i and SR Ca2+ content. Results: Ca2+-dependent, steady state INa/Ca density was increased in hypertrophied myocytes (P<0.05). Ca2+ release from the SR was also increased, whereas resting [Ca2+]i and the rate of decline of [Ca2+]i to control levels were unchanged. SR Ca2+ content, estimated by using 10.0 mmol/l caffeine, was also significantly increased in hypertrophied myocytes, but only when myocytes were held and stimulated from their normal resting potential (¿80 mV) but not from ¿40 mV. However, the rate of decline of caffeine-induced Ca2+ transients or INa/Ca was not significantly different between control and hypertrophied myocytes. Ca2+-dependence of INa/Ca, examined by comparing the slope of the descending phase of the hysteresis plots of INa/Ca vs. [Ca2+]i, was also similar in the two groups of cells. Conclusion: Data show that SR Ca2+ release and SR Ca2+ content were increased in hypertrophied myocytes, despite an increase in the steady state INa/Ca density. The observation that increased SR function occurred only when myocytes were stimulated from ¿80 mV suggests that Na+ influx may play a role in altering Ca2+ homeostasis in hypertrophied cardiac muscle, possibly through increased reverse Na+/Ca2+ exchange, particularly at low stimulation frequencies.

Yes / The Sphingosine-1-phosphate receptor 1 (S1PR1) and β1-adrenergic receptor (β1AR) are G protein-coupled receptors (GPCRs) expressed in the heart. These two GPCRs have opposing actions on adenylyl cyclase due to differential G protein-coupling. Importantly, both of these receptors can be regulated by the actions of GPCR kinase-2 (GRK2), which triggers desensitization and down-regulation processes. Although, classical signaling paradigms suggest that simultaneous activation of β1ARs and S1PR1s in a myocyte would simply be opposing action on cAMP production, in this report we have uncovered a direct interaction between these two receptors with a regulatory involvement of GRK2. In HEK293 cells overexpressing both β1AR and S1PR1, we demonstrate that β1AR down-regulation can occur after sphingosine 1-phosphate (S1PR1 agonist) stimulation while S1PR1 down-regulation can be triggered by isoproterenol (βAR agonist) treatment. This cross-talk between these two distinct GPCRs appears to have physiological significance since they interact and show reciprocal regulation in mouse hearts undergoing chronic βAR stimulation and also in a rat model of post-ischemic heart failure (HF). We demonstrate that restoring cardiac plasma membrane levels of S1PR1 produce beneficial effects counterbalancing deleterious β1AR overstimulation in HF.

Herbs have been used for many centuries in diverse civilizations for the treatment of heart disease. Only a few natural supplements claim to have direct cardiovascular actions including hawthorn (Crataegus spp.) and berberine derived from the Berberidaceae family. Several different studies indicate important cardiovascular effects of hawthorn and berberine. For example, both exert positive inotropic effects and have been used in the treatment of congestive heart failure. Recently, it was shown that hawthorn extract preparations cause negative chronotropic effects in a cultured neonatal murine cardiomyocyte assay independent of beta-adrenergic receptor blockade. The aim of this study was to further characterize the effect of hawthorn extract to decrease the contraction rate of cultured cardiomyocytes. We hypothesized that hawthorn extract may be acting through muscarinic receptors to decrease contraction rate of cardiomyocytes. Atrial and ventricular cardiomyocytes were treated with hawthorn extract in the presence of atropine or himbacine. Changes in the contraction rate of cultured cardiomyocytes revealed that both muscarinic antagonists significantly attenuated the negative chronotropic activity of hawthorn extract. Using quinuclidinyl benzilate, L-[benzylic-4,4'-3H] ([³H]-QNB) as a radioligand antagonist, the effect of a partially purified hawthorn extract fraction to inhibit muscarinic receptor binding was quantified. Hawthorn extract fraction 3 dose-dependently inhibited [³H]-QNB binding to mouse heart membranes. These findings suggest that muscarinic receptors may be involved in the negative chronotropic effect of hawthorn extracts in neonatal murine cardiomyocytes. Berberine exhibits variable positive and negative chronotropic effects in different species. Our first aim was to examine the effect of berberine in a cultured neonatal murine cardiomyocyte assay. Our study demonstrates that berberine has significant negative chronotropic actions on cardiomyocytes which is not an effect of beta-adrenergic receptor blockade. Pertussis toxin (PTX), a Gi/o protein inhibitor, blocked the negative chronotropic activity of berberine. Muscarinic, adenosine, opioid, and α₂ receptors are coupled through a G-protein (Gi/o) to adenylyl cyclase in an inhibitory fashion. Activation of these receptors are primarily responsible for PTX-sensitive negative chronotropic effects in heart. We hypothesized that berberine may be acting through one of these receptor type to decrease contraction rate of cardiomyocytes. For this purpose, we studied the effects of the muscarinic-receptor antagonists, atropine, himbacine, or AF- DX 116 on the negative chronotropic activity of berberine. Muscarinic antagonists completely blocked the effect of berberine on contraction rate of cardiomyocytes, whereas the bradycardic effect of berberine was not inhibited by the opioid, adenosine, or α2 receptor antagonists naloxone, CGS 15943, or phentolamine, respectively. Using [³H]QNB as a radioligand, we demonstrated that berberine bound to muscarinic receptors of adult mouse heart membranes with relatively high affinity. Furthermore, berberine dose-dependently inhibited [³H]QNB binding to muscarinic M2 receptors exogenously expressed in HEK 293 cells. Therefore, the findings of the present study suggest that berberine has muscarinic agonist effects in cultured neonatal murine cardiomyocytes, potentially explaining reported physiological effects of berberine. Cardiac hypertrophy represents the most important factor in the development of congestive heart failure. We investigated the inhibitory effect of berberine on hypertrophy of H9c2 cells. In rat heart-derived H9c2 myoblast cells treated with different hypertrophic agonists such as insulin growth factor II (IGF-II), arginine vasopressin (AVP), phenylephrine, and isoproterenol, protein content and size of cells were significantly increased compared to control group. However, the number of H9c2 cells after treatment with hypertrophic agonists did not differ significantly compared to control. The increases in area of cells and protein content induced by the hypertrophic agonists were inhibited by treatment with berberine in a concentration-dependent manner. Our findings have provided the first scientific evidence that berberine may have an inhibitory effect on hypertrophy of heart-derived cells, and provide a rationale for further studies to evaluate berberine's cardiac activity. / Graduation date: 2010

A sobrecarga crônica de pressão causa hipertrofia, disfunção e insuficiência cardíaca (IC). O mecanismo envolvido na transição da hipertrofia cardíaca compensada para descompensada ainda não é totalmente entendido. Evidências sugerem que modificações nas proteínas contráteis poderiam contribuir para disfunção contrátil e evolução para IC. Neste sentido, estudos mostraram mudanças na expressão das proteínas da maquinaria contrátil durante o desenvolvimento da doença cardíaca como um mecanismo inicialmente benéfico. Porém, na insuficiência cardíaca, ocorrem alterações estruturais que prejudicam a contratilidade. Contudo, não se sabe ao certo quais proteínas estariam contribuindo para a transição da hipertrofia compensada para a insuficiência cardíaca. Este estudo teve como objetivo investigar as alterações das proteínas da maquinaria contrátil na transição da hipertrofia cardíaca compensada para descompensada e correlacionar essas alterações com a função cardíaca. Ratos Wistar machos foram submetidos a estenose da aorta abdominal. Após 90d da cirurgia, foram realizados ecocardiograma, análise da pressão sanguínea e os corações foram coletados para realização do Western blot e imunofluorescência para miosina de cadeia pesada, actina sarcomérica, troponina T e troponina I. Os dados foram considerados significantes quando p<0,05. Aos 90d, 70,0±5,35% dos animais apresentaram hipertrofia cardíaca (HH) e 30,3±4,79% corações hipertrofiados+dilatados (HD). A pressão arterial média aumentou 58,2% no HH e 55,0% no HD. As? expressões? de? ?-actina sarcomérica, miosina de cadeia pesada, troponina T e I aumentaram no grupo HH. No grupo HD, a miosina de cadeia pesada e a troponina T reduziram significantemente. A função sistólica manteve-se preservada nos grupos controle e HH, porém reduzida no HD. A perda estrutural da miosina de cadeia pesada e da troponina T poderia contribuir para a insuficiência cardíaca observada nesse modelo experimental. / Hypertension causes hypertrophy, cardiac dysfunction and heart failure (HF). The mechanisms implicated in the transition from compensated to decompensated cardiac hypertrophy are not fully understood. There is considerable evidence that changes in the contractile proteins may contribute to the contractile dysfunction and progression to HF. Studies have shown changes in the expression of contractile proteins during the development of heart disease as a mechanism that is initially beneficial. However, in heart failure there is an intrinsic reduction of cross-bridges that contributes to impaired contractility. It is not known which proteins are contributing to the transition from compensated hypertrophy to heart failure. We investigated ?-sarcomeric actin, heavy chain myosin and troponins T and I in the transition from compensated to decompensated cardiac hypertrophy and correlate these alterations with cardiac function. Male Wistar rats were submitted to abdominal aorta constriction and killed at 90 days post-surgery (dps). The hearts were collected; Western blot and immunofluorescence were performed to investigate ?-sarcomeric actin, heavy chain myosin and troponins T and I. Blood pressure and cardiac systolic function were evaluated. Data were considered significant when p<0.05. At 90 dps, 70,0±5,35% presented hypertrophic hearts (HH) and 30,3±4,79% hypertrophic+dilated hearts (HD). Mean blood pressure increased 58.19% in HH and 54.96% in HD. Heavy chain myosin, troponin T, troponin I and ?-sarcomeric actin expression increased in HH. In HD, only heavy chain myosin and troponin T reduced significantly. The systolic function was the same in control and HH animals and reduced in HD. The structural loss of heavy chain myosin and troponin T could contribute to heart failure observed in this experimental model of abdominal aorta constriction.

Tao Kin Pong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 144-152). / Abstracts in English and Chinese. / Chapter i. --- Cover page --- p.1 / Chapter ii. --- Table of contents --- p.2 / Chapter iii. --- Abstract of thesis (English version and Chinese Version) --- p.4 / Chapter iv. --- Acknowledgements --- p.8 / Chapter v. --- Abbreviations --- p.9 / Chapter 1. --- Introduction / Interstitial tissue and Leydig cells --- p.11 / Seminiferous tubules --- p.11 / "Male germ cell line and spermatogenesis (Mitotic, Meiotic and Post-meiotic)" --- p.12 / Sertoli cells --- p.14 / Specialized organizations of junction present in testis --- p.15 / Dynamic nature of Sertoli-Sertoli & Sertoli-germ cell junctions --- p.16 / Role of proteases and protease inhibitors in male gametogenesis --- p.17 / Proteases and Proteases Inhibitors expressed in testis --- p.18 / Hormonal control of spermatogenesis --- p.19 / Hypothyroidism and testis development --- p.21 / Genes to be studied: / Proteases --- p.22 / Proteases Inhibitors --- p.27 / Other spermatogenesis related genes --- p.30 / Chapter 2. --- Objectives --- p.32 / Chapter 3. --- Materials and Methods / Animal treatments and tissue collection --- p.33 / RNA preparation --- p.34 / RT-PCRs --- p.35 / Real-time PCRs --- p.35 / Data manipulations and Statistics --- p.36 / Primer sequences used in this experiment --- p.37 / Chapter 4. --- Results / "Effect of neonatal hypothyroidism on developmental profile of body weight, absolute and relative testicular weight" --- p.40 / Developmental transcription profiles of genes under normal and hypothyroidism --- p.43 / Screening Data --- p.78 / Expression of non-spermatogenic genes at neonatal age --- p.88 / Responsiveness of gene transcription after thyroxin replacement --- p.89 / Changes of gene expression under different hypothyroid regimens --- p.97 / Chapter 5. --- Discussion / Changes in testicular size under hypothyroidism --- p.107 / Five patterns of transcription profile --- p.107 / "Suggestion on the role of ""MEIOTIC"" proteases and inhibitors" --- p.111 / "Suggestion on the role of ""POST-MEIOTIC"" proteases and inhibitors" --- p.113 / "Explanations on ""SOMATIC"" genes" --- p.114 / "Explanations on ""MITOTIC"" genes" --- p.115 / Explanations on the un-clustered pattern --- p.116 / Explanations on the age down-regulated group --- p.116 / Proposed clustering of genes according to their transcription profile --- p.117 / "Expression of some ""non-spermatogenic"" genes before puberty" --- p.123 / Neonatal hypothyroidism as a model for studying reproductive physiology --- p.125 / Different components of spermatogenesis --- p.127 / Chapter I. --- Roles of nuclear and chromatin related genes in assisting meiosis --- p.128 / Chapter II. --- Roles of specific transcription regulators in assisting gene selection --- p.129 / Chapter III. --- Role of signal transduction molecules for translation and activation --- p.131 / Chapter IV. --- Role of proteases and inhibitors for matrix and junctions dynamics --- p.132 / The somatic proteases and inhibitors system in the testis --- p.133 / Spermatogenic proteases and inhibitors system --- p.134 / Chapter V. --- Role of matrix and junctional molecules in intercellular interactions --- p.137 / Chapter VI. --- Role of cytoplasmic motors in cellular movement --- p.139 / Chapter 6. --- Conclusion / Proposed story of spermatogenesis - involvement of proteases and inhibitors --- p.140 / Future Direction --- p.141 / Chapter 7. --- References --- p.144

A sobrecarga crônica de pressão causa hipertrofia, disfunção e insuficiência cardíaca (IC). O mecanismo envolvido na transição da hipertrofia cardíaca compensada para descompensada ainda não é totalmente entendido. Evidências sugerem que modificações nas proteínas contráteis poderiam contribuir para disfunção contrátil e evolução para IC. Neste sentido, estudos mostraram mudanças na expressão das proteínas da maquinaria contrátil durante o desenvolvimento da doença cardíaca como um mecanismo inicialmente benéfico. Porém, na insuficiência cardíaca, ocorrem alterações estruturais que prejudicam a contratilidade. Contudo, não se sabe ao certo quais proteínas estariam contribuindo para a transição da hipertrofia compensada para a insuficiência cardíaca. Este estudo teve como objetivo investigar as alterações das proteínas da maquinaria contrátil na transição da hipertrofia cardíaca compensada para descompensada e correlacionar essas alterações com a função cardíaca. Ratos Wistar machos foram submetidos a estenose da aorta abdominal. Após 90d da cirurgia, foram realizados ecocardiograma, análise da pressão sanguínea e os corações foram coletados para realização do Western blot e imunofluorescência para miosina de cadeia pesada, actina sarcomérica, troponina T e troponina I. Os dados foram considerados significantes quando p<0,05. Aos 90d, 70,0±5,35% dos animais apresentaram hipertrofia cardíaca (HH) e 30,3±4,79% corações hipertrofiados+dilatados (HD). A pressão arterial média aumentou 58,2% no HH e 55,0% no HD. As? expressões? de? ?-actina sarcomérica, miosina de cadeia pesada, troponina T e I aumentaram no grupo HH. No grupo HD, a miosina de cadeia pesada e a troponina T reduziram significantemente. A função sistólica manteve-se preservada nos grupos controle e HH, porém reduzida no HD. A perda estrutural da miosina de cadeia pesada e da troponina T poderia contribuir para a insuficiência cardíaca observada nesse modelo experimental. / Hypertension causes hypertrophy, cardiac dysfunction and heart failure (HF). The mechanisms implicated in the transition from compensated to decompensated cardiac hypertrophy are not fully understood. There is considerable evidence that changes in the contractile proteins may contribute to the contractile dysfunction and progression to HF. Studies have shown changes in the expression of contractile proteins during the development of heart disease as a mechanism that is initially beneficial. However, in heart failure there is an intrinsic reduction of cross-bridges that contributes to impaired contractility. It is not known which proteins are contributing to the transition from compensated hypertrophy to heart failure. We investigated ?-sarcomeric actin, heavy chain myosin and troponins T and I in the transition from compensated to decompensated cardiac hypertrophy and correlate these alterations with cardiac function. Male Wistar rats were submitted to abdominal aorta constriction and killed at 90 days post-surgery (dps). The hearts were collected; Western blot and immunofluorescence were performed to investigate ?-sarcomeric actin, heavy chain myosin and troponins T and I. Blood pressure and cardiac systolic function were evaluated. Data were considered significant when p<0.05. At 90 dps, 70,0±5,35% presented hypertrophic hearts (HH) and 30,3±4,79% hypertrophic+dilated hearts (HD). Mean blood pressure increased 58.19% in HH and 54.96% in HD. Heavy chain myosin, troponin T, troponin I and ?-sarcomeric actin expression increased in HH. In HD, only heavy chain myosin and troponin T reduced significantly. The systolic function was the same in control and HH animals and reduced in HD. The structural loss of heavy chain myosin and troponin T could contribute to heart failure observed in this experimental model of abdominal aorta constriction.

[Truncated abstract] The innate ability of the heart to compensate for an increase in workload as a result of disease or injury, through an increase in size and mass is known as cardiac hypertrophy. The hypertrophy of the heart compensates for an increase in workload with an increase in cardiac output. However, excessive hypertrophy can result in cardiac dysfunction and substantially increases the risk of cardiac failure and mortality. The molecular mechanisms that regulate the development of cardiac hypertrophy and cardiac failure are not entirely understood. Traditionally, the G-protein Coupled Receptor (GPCR) and the downstream Mitogen-Activated Protein Kinase (MAPK) family of proteins have been implicated. However, elevated circulating and ventricular levels of several classes of cytokines also suggested that signaling by the downstream effectors of cytokine receptors, such as the Signal Transducers and Activators of Transcription (STATs), may be important. The aim of this thesis was, therefore, to characterize the involvement of MAPK and STAT pathways in regulating cardiac hypertrophy and cardiac failure. A function for MAPK and STAT signaling in regulating cardiac hypertrophy stimulated by the inflammatory cytokine IL-1Β was initially defined in primary cultures of neonatal rat cardiac myocytes. In this study, it was demonstrated that the chemical inhibition of ERK or p38MAPK was sufficient to inhibit IL-1Β-stimulated ANF expression. In contrast, simultaneous inhibition of both ERK and p38MAPK was required to ablate the hypertrophic morphology of cardiac myocytes treated with IL-1Β. These results demonstrated differential signaling from the MAPK isoforms in regulating the gene expression and morphological components of cardiac hypertrophy. In addition, it was revealed that IL-1Β treatment resulted in a delayed response (>60 min) in STAT3α tyrosine phosphorylation, which was subsequently shown to require the initial rapid activation of either ERK or p38MAPK. IL-1Β-stimulated STAT3 phosphorylation was also dependent on the de novo synthesis of secondary signaling molecules. The ablation of the STAT3 tyrosine phosphorylation by the inhibition of ERK or p38MAPK activity, correlated with the attenuation of IL-1Β-stimulated ANF expression, suggesting that signaling through STAT3α may be involved in regulating gene expression associated with IL-1Β cardiac hypertrophy

[Truncated abstract] The enlargement of the heart, also known as myocardial hypertrophy, is thought to be a compensatory process that maintains the mechanical function of the heart in response to stress factors such as pressure or volume overload. Although this process is initially compensatory, it frequently results in heart failure and death. Cardiac hypertrophy is a complex process involving changes in the individual cardiac muscle cells, cardiac myocytes. As well as the morphological changes that result from hypertrophy, there are molecular changes within each cell that regulate the hypertrophic process. These molecular changes involve many different pathways within the cardiac myocytes and remain poorly understood . . . Both STAT3α and β overexpression resulted in the upregulation of the VEGF, MnSOD and SOCS-3 genes. This indicates that in the heart, STAT3β is able to activate the gene expression of these genes in a similar manner to STAT3α. However, STAT3α or β activation alone is not enough to induce cardiac hypertrophy. In conclusion, the results presented in this thesis determined a novel role for ERK in the induction of cell death in the heart and revealed many changes in cardiac gene expression following ERK activation. These genes may be the mediators of ERK responses and their identification provides valuable information and direction for further research in this area. One consequence of ERK activation was the negative regulation of the STAT3 pathway. Further investigation revealed for the first time that the STAT3 proteins themselves may not be involved in the induction of cardiac hypertrophy and that STAT3β, initially thought to be a transcriptional repressor, can induce the expression of genes that are known to be activated by STAT3α in the heart. Therefore, these results help to better understand the roles of these two signalling pathways in the heart.

Thesis (Ph.D.)--University of Alabama at Birmingham, 2008. / Title from PDF title page (viewed on July 16, 2010). Includes bibliographical references.